DESCRIPTION: Protection against oxidant factors is provided by antioxidants including glutathione (GSH)-dependent enzymes. Exposure to oxidative stress induces antioxidant enzymes including these GSH-dependent enzymes. Detailed biochemical studies on the oxidative induction of enzymes has been accomplished, yet little is known about regulation at a molecular level. This proposal is directed toward regulation of the nonclassical selenium-dependent GSH peroxidases (ncGPXs) gastrointestinal (GPX2), plasma-associated (GPX3), and phospholipid hydroperoxide (GPX4). Response of these GPX genes and their regulatory proteins to exogenous oxidative stress will be characterized. Studies include structural characterization of ncGPXs genes by sequencing 5 and 3 flanking regions, determining mRNA initiation sites, and locating basal promoter regions. Inducible promoter regions of each gene will be identified using a series of 5-deletion promoter constructs and individual positive and negative regulatory elements identified by functional and structural studies. Response of these elements to a variety of oxidants will be determined. Other studies will investigate the functional role of a unique stem-loop element present in the 5 untranslated regions of all GPXs through use of a series of mini-gene and chimeric constructs, to determine if a regulatory mechanism common to all GPXs exists. Information obtained about the regulatory mechanism of the enzymes can be used to study their protective role in a variety of human diseases and against environmental toxins, as well as determine if common regulatory mechanism(s) exist for all GSH-dependent enzymes.